Computer-aided automation is currently used for pre-press operations used in developing and publishing photo-ad periodicals, specialized magazines and video catalogs. Automation of pre-press operations is essential where large volumes of photographs and text must be accumulated, sorted, half-toned, sized, paginated and printed over a short deadline. Various publishing software programs are available to automate these pre-press operations.
One important aspect of pre-press operations is the step of using a scanner to scan a color image from photographs, videos, and prints. Scanning results in the color image being divided into a plurality of pixels with each pixel forming one segment of the color image. The pixels usually have differing colors and the color of each pixel is identified by a color value which can be digitally stored within a memory such as is typically associated with a computer.
Scanners of the prior art typically use RGB values located within an RGB color space to identify the color of the pixels of a color image. An RGB color space is a cubic or color-component color space with each RGB value having a red, green, and blue component for identifying the amount of each color component in a pixel. Combining the amount of red, green, and blue color identified by the color components produces the color of the pixel identified. Other cubic or color-component color spaces, such as YMC (yellow, magenta, cyan) color space or a YMCK (yellow, magenta, cyan and black) color space, can be used to identify the color values of pixels. As used in this patent application, a cubic color space refers to a three-dimensional color space having three different-colored components that identify the amount of a particular color in a pixel.
Once digitized, the color image of a photograph can be displayed on a computer screen and the color values manipulated to make color corrections to the image. A corrected color image can then be printed by directing the corrected color values of the pixels to a four-color printer. Methods for scanning color images, providing limited correction of the color image by manipulating color values and for printing a reproduction of the color image based on the color values are known in the prior art.
There are problems, however, with the prior art methods for scanning, color correcting, and printing reproductions of color images. In order to make a color correction, the particular colors in the color image to be altered must be selected. In prior art systems complicated functions must be used by an operator to select the colors to corrected. Because of the difficulty in selecting colors, the operator must have a high level of expertise and must undertake a time-consuming process to make a desired color correction to a color image.
Another problem associated with scanning color images and printing reproductions of scanned images is the occurrence of undesired muddiness in the print due to excess amounts of the hue-inks being used to print mere gray scale darkness. An improved color image reproducing method and apparatus are needed that will enable an operator to more easily select the colors to be corrected and then to make the desired corrections. Also needed are improved methods and apparatus to properly use a black ink in the four color printing to provide gray scale components and good definition, including removal of gray components from the other inks and replacement with suitable amounts of black.